Bacteria, Archaea and eukaryotes

Microbial world has three main cell lineages within it all of that are thought to have evolved from a single progenitor in Figure. The lineages are formally identified as domains and were recognized from the DNA sequence of genes common to all organisms Section B3. The three domains are the Bacteria previously called the Eubacteria, the   Archaea previously called   the   Archaeabacteria and   Eukarya. The defining property of the Eukarya compared to the Bacteria and Archaea is the presence of a nucleus. This is convenient to group the annucleate lineages the Bacteria and Archaea together as the prokaryotes. Prokaryotes are  with  a very few exceptions Section C6 all microorganisms but  the  Eukarya include not  only  microbial chlorophyta,  fungi, and  protists Sections H and  I but  also  macroorganisms like as higher animals and  plants.

                                          Figure  1:  The three cell lineages evolved from a common ancestor.

The Prokaryotic cell structure is characterized through the absence of a nucleus but it also lacks energy-generating organelles like as chloroplasts and mitochondria. Instead, prokaryotes generate energy through cytoplasmic substrate-level phosphorylation and oxidative phosphorylation across their cell membranes Section E. Separately from these major differences, there are a multitude of distinctive physiological properties and biochemical, the most important of that are listed in Table 1. The differences which exist among the Archaea and the Bacteria Section C6 are discussed elsewhere in more detail.